Enable IsolatedCodeCache feature by default

IsolatedCodeCache feature has been on finch trial since 71 and the
results are as expected. No measurable regressions on the top-level
loading metrics and an expected regression of ~7-10% on the time spent
compiling Javascript. The regression is expected because we do not share
the compiled code across different origins.

Bug: chromium:812168
Change-Id: Ib0aec9def0be83ae59298adc8516979b7587ae27
Reviewed-on: https://chromium-review.googlesource.com/c/1337625
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608784}

net/base/features.cc

@@ -12,7 +12,7 @@ namespace features {
 // to site-isolated code cache are handled by the content/GeneratedCodeCache
 // When this flag is enabled, the metadata field of the HttpCache is unused.
 const base::Feature kIsolatedCodeCache = {"IsolatedCodeCache",
-                                          base::FEATURE_DISABLED_BY_DEFAULT};
+                                          base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables the additional TLS 1.3 server-random-based downgrade protection
 // described in https://tools.ietf.org/html/rfc8446#section-4.1.3

net/http/http_cache_unittest.cc

@@ -9662,6 +9662,9 @@ TEST_F(HttpCacheTest, InvalidLoadFlagCombination) {
 // Tests that we can read metadata after validating the entry and with READ mode
 // transactions.
 TEST_F(HttpCacheTest, ReadMetadata) {
+  base::test::ScopedFeatureList feature_list;
+  feature_list.InitAndDisableFeature(net::features::kIsolatedCodeCache);
+  ASSERT_FALSE(base::FeatureList::IsEnabled(net::features::kIsolatedCodeCache));
   MockHttpCache cache;
 
   // Write to the cache

third_party/WebKit/LayoutTests/flag-specific/site-per-process/http/tests/devtools/isolated-code-cache/cross-origin-test-expected.txt

+Tests V8 code cache for javascript resources
+
+---First navigation - produce and consume code cache ------
+
+v8.compile Properties:
+{
+    data : {
+        columnNumber : 0
+        lineNumber : 0
+        notStreamedReason : "script too small"
+        streamed : <boolean>
+        url : .../devtools/resources/v8-cache-script.js
+    }
+    endTime : <number>
+    startTime : <number>
+    type : "v8.compile"
+}
+Text details for v8.compile: v8-cache-script.js:1
+v8.compile Properties:
+{
+    data : {
+        columnNumber : 0
+        lineNumber : 0
+        notStreamedReason : "already used streamed data"
+        streamed : <boolean>
+        url : .../devtools/resources/v8-cache-script.js
+    }
+    endTime : <number>
+    startTime : <number>
+    type : "v8.compile"
+}
+Text details for v8.compile: v8-cache-script.js:1
+v8.compile Properties:
+{
+    data : {
+        cacheProduceOptions : "code"
+        columnNumber : 0
+        lineNumber : 0
+        notStreamedReason : "already used streamed data"
+        producedCacheSize : <number>
+        streamed : <boolean>
+        url : .../devtools/resources/v8-cache-script.js
+    }
+    endTime : <number>
+    startTime : <number>
+    type : "v8.compile"
+}
+Text details for v8.compile: v8-cache-script.js:1
+v8.compile Properties:
+{
+    data : {
+        cacheConsumeOptions : "code"
+        cacheRejected : false
+        columnNumber : 0
+        consumedCacheSize : <number>
+        lineNumber : 0
+        notStreamedReason : "already used streamed data"
+        streamed : <boolean>
+        url : .../devtools/resources/v8-cache-script.js
+    }
+    endTime : <number>
+    startTime : <number>
+    type : "v8.compile"
+}
+Text details for v8.compile: v8-cache-script.js:1
+
+--- Second navigation - from a different origin ------
+
+v8.compile Properties:
+{
+    data : {
+        columnNumber : 0
+        lineNumber : 0
+        notStreamedReason : "script too small"
+        streamed : <boolean>
+        url : .../devtools/resources/v8-cache-script.js
+    }
+    endTime : <number>
+    startTime : <number>
+    type : "v8.compile"
+}
+Text details for v8.compile: v8-cache-script.js:1
+